In the past sales at on-line retailers have surpassed the totals of the year before. Computer users have become more and more comfortable reviewing products on the internet and having them delivered via mail order. Often, such purchases are paid for using credit cards. Such an approach may be convenient, such as when buying a large item from an established retailer. Other transactions lend themselves more toward on-line payment processing systems (which themselves may involve credit card companies or by other mechanisms). For example, transactions may be paid for through open payment systems such as Google Checkout or PayPal, such as when the person providing the product or service (the merchant or vendor) does not accept credit cards; or the buyer doesn't want to provide credit card information directly to the merchant or vendor due to lack of trust; or the buyer doesn't want to create an account at each different merchant or vendor. Other types of purchases may also be carried out using such payment systems.
More than one party can be associated with a purchase transaction. For example, a manager may be required to approve a purchase transaction of an item that a salesperson wishes to purchase. In this case, the manager may have to purchase the item himself because the manager may not be capable of approving the purchase if the salesperson places the order.